Articular ultrasonography: interobserver reliability in rheumatoid arthritis

Ultrasonography (US) has a recent use in Rheumatology, and the reliability of the method in rheumatoid arthritis (RA) patients has yet to be clarified.

To test, in a RA survey, the reproducibility of musculoskeletal US performed by rheumatologists with one-year training through re-analysis by a Rheumatologist experienced in the method.

This cross-sectional study included consecutive RA patients from our tertiary center. US exam was performed in metacarpophalangeal joints, proximal interphalangeal joints, and wrists. Presence of synovitis, power Doppler (PD) signal, bone erosions, and cartilage changes comprised the US parameters evaluated. A kappa value in-between 0.20 and 0.40 was considered fair; in-between 0.41 and 0.60 was moderate; in-between 0.61 and 0.80 was good; and above 0.81 was excellent.

We analyzed 1,380 joints of 60 RA patients (78% females, 78% caucasoids). Mean age was 58 ± 11.56 years, mean disease duration was 9.98 ± 7.79 years, mean DAS28 was 3.82 ± 1.53, and mean HAQ was 0.91 ± 0.67. Kappa agreement for synovitis ranged from 0.30 to 0.70; for PD signal, from 0.53 to absolute agreement; for erosions, from 0.70 to 0.97; for cartilage changes, from 0.28 to 0.63.

Although good, moderate and excellent interobserver agreement were obtained for erosions and PD, concordance for synovitis and cartilage changes were less impressive in our patients with active RA. Further studies on standardization of scanning technique are necessary to improve musculoskeletal US reproducibility.